Palaeoproterozoic to Eoarchaean crustal growth in southern Siberia: a Nd-isotope synthesis

Nd-isotope analyses from 114 rock samples are reported from the southern part of the Siberian craton to establish a first-order crustal formation scheme for the region. The Nd-isotopedata show considerable variability within and among different cratonic units. In many cases this variability reflects differing degrees of mixing between juvenile and older (up to Eoarchaean) crustal components. The fragments of Palaeoproterozoic juvenile crust within the studied segment of the Siberian craton margin have Nd-model ages of 2.0-2.3 Ga. Voluminous Palaeoproterozoicgranites ( 1.85 Ga) were intruded into cratonic fragments and suture zones. These granites mark the stabilization of the southern Siberian craton. The complexity in the Nd data indicatea long history of crustal development, extending from the Eoarchaean to the Palaeoproterozoiceras, which is interpreted to reflect the amalgamation of distinct Archaean crustal fragments, with differing histories, during Palaeoproterozoic accretion at 1.9-2.0 Ga and subsequent cratonic stabilization at 1.85 Ga. Such a model temporally coincides with important orogenic events on nearly every continent and suggests that the Siberian craton participated in the formation of a Palaeoproterozoic supercontinent at around 1.9 Ga

К 100ЛЕТИЮ СО ДНЯ РОЖДЕНИЯ ЧЛЕНА-КОРРЕСПОНДЕНТА АН СССР МИХАИЛА МИХАЙЛОВИЧА ОДИНЦОВА

This article provides basic information about Mikhail M. Odintsov (1911–2011), Corresponding Member of the USSR Academy of Sciences, and his scientific, organizational and social activities. From 1954 to 1976, he was the founder and director of the Institute of Geology of the East Siberian Branch of the USSR Academy of Sciences, which is now world known as the Institute of Earth's Crust of the Siberian Branch of the Russian Academy of Sciences. The Institute was awarded with two Orders of Lenin (in 1963, and in 1971), and the Order of Red Banner of Labour (1975). In 2011, the scientific community in Russia celebrates the 100th anniversary of Mikhail M. Odintsov.В статье приведены основные сведения о научной, научно-организационной и общественной деятельности члена-корреспондента АН СССР М.М. Одинцова (1911–2011 гг.) – одного из основателей и руководителей (1954–1976 гг.) Института геологии Восточно-Сибирского филиала АН СССР – Института земной коры СО АН, награжденного орденами Ленина (1963 г., 1971 г.) и орденом Трудового Красного Знамени (1975 г.), столетие со дня рождения которого отечественная геологическая общественность отмечает в 2011 г

ДЕСЯТОЕ ЮБИЛЕЙНОЕ ВСЕРОССИЙСКОЕ НАУЧНОЕ СОВЕЩАНИЕ «ГЕОДИНАМИЧЕСКАЯ ЭВОЛЮЦИЯ ЛИТОСФЕРЫ ЦЕНТРАЛЬНО-АЗИАТСКОГО ПОДВИЖНОГО ПОЯСА: ОТ ОКЕАНА К КОНТИНЕНТУ» (ИЗК СО РАН, 17–20 ОКТЯБРЯ 2012 Г.)

The article provides review about the 10th anniversary of All-Russia scientific conference «Geodynamic evolution of the lithosphere of the Central Asian Orogenic Belt: from ocean to continent», which was held on 17–20 October, 2012 at the Institute of the Earth’s Crust SB RAS in Irkutsk, Russia.В статье приводится информация о десятом юбилейном Всероссийском научном совещании «Геодинамическая эволюция литосферы Центрально-Азиатского подвижного пояса: от океана к континенту», которое проходило в Институте земной коры Сибирского отделения Российской академии наук (г. Иркутск) с 17 по 20 октября 2012 года

ВАЛЕНТИН СЕРГЕЕВИЧ ФЕДОРОВСКИЙ – КОРИФЕЙ CИБИРСКОЙ ГЕОЛОГИИ

The publication is devoted to the 80 anniversary of Valentin S. Fedorovsky, the coryphaeus of Siberian geology.Cтатья посвящена 80-летнему юбилею Валентина Сергеевича Федоровского, корифея Сибирской геологии

КОМПЛЕКСЫ МЕТАМОРФИЧЕСКИХ ЯДЕР ЗАБАЙКАЛЬЯ: ОБЗОР

Metamorphic core complexes (hereafter MCC) revealed in the Transbaikalia have similar features of their patterns. Three levels can be distinguished by structural­material indicators: core, zone of mylonites (dynamically metamorphosed rocks) and overlying formations. The cores are composed of the Paleozoic granites and granitogneisses. Zones of mylonites skirt the cores and are characterized by various tectonites which are formed at the expense of the core rocks. The overlying formations include volcanogenic­sedimentary series of the Mesozoic and the Upper Palaeozoic. The rocks are not metamorphosed, yet subject to brittle deformations. Structurally, they are detached and deposited above the zone of mylonites.In Transbaikalia, MCC are characterized by synmetamorphic structural paragenesises of one type: low­angle schistosity, micro­ and macro­structures (folds, mineral streaking, boudinage, pressure shadows, C–S structure, kick­bends). According to the kinematic analyses, they were formed by the simple shear mechanism along the zones of deeply penetrating regional dislocations which plunged in the south­eastward direction. Tectonic transportation of the materials developed in the same direction, i.e. the top parts of tectono­stratigraphic sections were displaced against the lower parts in the south­eastward direction. Extension deformations tended in the north­west – south­east direction. Such movements facilitated formation of synthetic listric normal faults and rift basins. The most intensive tectonic exposure period is determined as 112–123 mln years, while the period of metamorphism is assessed as 140–130 mln years. The rocks in depth of the deep dislocation were transformed in conditions of amphibole facies of metamorphism (Т=590–640 °С; Р=3.2–4.6 kbar).According to our structural-­geological, petrological and isotopic data, the age of the majority of the metamorphic formations of the Transbaikalia is determined as the Late Mesozoic. They were formed in the extension regime due collapse of the Late Mesozoic orogeny, that was caused by accretion­collision events during the Early Mesozoic. Thickening of the continental crust contributed to increase of heat flow and higher plasticity at the crustal bottom. The orogen was thus unstable and flowing and caused regional extension and dislocations at the middle­crust level. Thinning of the crust was accompanied by isostatic uplifting which facilitated emergence of the structural metamorphic complexes of the middle­crust levels on the surface and formation of the metamorphic core complexes.Установленные в Забайкалье комплексы метаморфических ядер (metamorphic core complexes – МСС) характеризуются близкими чертами строения. По структурно-вещественным признакам в них выделяются три структурных уровня: ядро, зона милонитов (динамометаморфизованных пород) и образования покрова. Ядра сложены палеозойскими гранитами и гранитогнейсами. Милониты окаймляют ядра и характеризуются разнообразными тектонитами, возникшими за счет пород ядра. К покровным образованиям относятся вулканогенно-осадочные серии мезозоя и верхнего палеозоя. Породы не метаморфизованы, но подвержены хрупким деформациям. Располагаются они структурно выше зоны милонитов, отделяясь от них детачментом.Для МСС Забайкалья характерны однотипные синметаморфические структурные парагенезисы: пологая сланцеватость, микро- и макроструктуры (складки, линейность, будинаж, тени давления, C–S-структуры, кинкбанды). Кинематический анализ указывает, что их становление происходило по механизму простого сдвига по зонам глубокопроникающих региональных срывов, погружавшихся в юго-восточном направлении. В этом же направлении осуществлялся тектонический транспорт вещества, т.е. верхние части тектоностратиграфических разрезов относительно нижних смещались на юго-восток. Деформация растяжения характеризовалась трендом северо-запад – юго-восток. Такие движения способствовали возникновению синтетических листрических сбросов и формированию  рифтовых впадин. Время наиболее интенсивного тектонического экспонирования определяется значениями 112 – 123 млн лет, а время проявления метаморфизма – 140–130 млн лет. Породы в зоне глубинного срыва были преобразованы в условиях амфиболитовой фации метаморфизма (Т=590–640 °С и Р=3.2–4.6 кбар).Структурно-геологические, петрологические и изотопные данные показывают, что значительная часть метаморфических образований Забайкалья имеет позднемезозойский возраст. Их формирование происходило в режиме растяжения и связано с коллапсом позднемезозойского орогена, который возник в процессе раннемезозойских аккреционно-коллизионных событий. Утолщение континентальной коры способствовало усилению теплового потока и повышению пластичности в низах коры. Это предопределило неустойчивость орогена и его растекание, что привело к возникновению регионального растяжения и срывов на среднекоровом уровне. Утонение коры сопровождалось изостатическим поднятием, что способствовало выводу на поверхность структурновещественных комплексов среднекоровых уровней и формированию комплексов метаморфических ядер

Linking collisional and accretionary orogens during Rodinia assembly and breakup: Implications for models of supercontinent cycles

Periodic assembly and dispersal of continental fragments has been a characteristic of the solid Earth for much of its history. Geodynamic drivers of this cyclic activity are inferred to be either top-down processes related to near surface lithospheric stresses at plate boundaries or bottom-up processes related to mantle convection and, in particular, mantle plumes, or some combination of the two. Analysis of the geological history of Rodinian crustal blocks suggests that internal rifting and breakup of the supercontinent were linked to the initiation of subduction and development of accretionary orogens around its periphery. Thus, breakup was a top-down instigated process. The locus of convergence was initially around north-eastern and northern Laurentia in the early Neoproterozoic before extending to outboard of Amazonia and Africa, including Avalonia–Cadomia, and arcs outboard of Siberia and eastern to northern Baltica in the mid-Neoproterozoic (~760 Ma). The duration of subduction around the periphery of Rodinia coincides with the interval of lithospheric extension within the supercontinent, including the opening of the proto-Pacific at ca. 760 Ma and the commencement of rifting in east Laurentia. Final development of passive margin successions around Laurentia, Baltica and Siberia was not completed until the late Neoproterozoic to early Paleozoic (ca. 570–530 Ma), which corresponds with the termination of convergent plate interactions that gave rise to Gondwana and the consequent relocation of subduction zones to the periphery of this supercontinent. The temporal link between external subduction and internal extension suggests that breakup was initiated by a top-down process driven by accretionary tectonics along the periphery of the supercontinent. Plume-related magmatism may be present at specific times and in specific places during breakup but is not the prime driving force. Comparison of the Rodinia record of continental assembly and dispersal with that for Nuna, Gondwana and Pangea suggests grouping into two supercycles in which Nuna and Gondwana underwent only partial or no break-up phase prior to their incorporation into Rodinia and Pangea respectively. It was only after this final phase of assembly that the supercontinents then underwent full dispersal

TO THE 100TH ANNIVERSARY OF MIKHAIL M. ODINTSOV, CORRESPONDING MEMBER OF THE USSR ACADEMY OF SCIENCES

This article provides basic information about Mikhail M. Odintsov (1911–2011), Corresponding Member of the USSR Academy of Sciences, and his scientific, organizational and social activities. From 1954 to 1976, he was the founder and director of the Institute of Geology of the East Siberian Branch of the USSR Academy of Sciences, which is now world known as the Institute of Earth's Crust of the Siberian Branch of the Russian Academy of Sciences. The Institute was awarded with two Orders of Lenin (in 1963, and in 1971), and the Order of Red Banner of Labour (1975). In 2011, the scientific community in Russia celebrates the 100th anniversary of Mikhail M. Odintsov

THE 10TH ANNIVERSARY ALLRUSSIA SCIENTIFIC CONFERENCE «GEODYNAMIC EVOLUTION OF THE LITHOSPHERE OF THE CENTRAL ASIAN OROGENIC BELT: FROM OCEAN TO CONTINENT» (IEC SB RAS, 17–20 OCTOBER, 2012)

The article provides review about the 10th anniversary of All-Russia scientific conference «Geodynamic evolution of the lithosphere of the Central Asian Orogenic Belt: from ocean to continent», which was held on 17–20 October, 2012 at the Institute of the Earth’s Crust SB RAS in Irkutsk, Russia

Introduction to special issue: Geology of the Lake Baikal region

International audienc

FEDOROVSKY, VALENTIN S. – THE CORYPHAEUS OF SIBERIAN GEOLOGY

The publication is devoted to the 80 anniversary of Valentin S. Fedorovsky, the coryphaeus of Siberian geology